1. Field of the Invention
Embodiments of the present invention relate to a transflective (transmitting-reflective) type liquid crystal display panel and a method of fabricating the same, and more particularly, to a transflective type liquid crystal display panel which can realize a uniform gray scale value in a pixel region by matching a reflective curve and a transmitting curve through a coupling capacitor in a reflective part of pixel region.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) device displays images by controlling light transmittance of liquid crystal with the use of electric field. This liquid crystal display device is largely classified into a vertical electric field applying mode and a horizontal electric field applying mode according to a direction of electric field to drive liquid crystal.
The vertical electric field applying mode liquid crystal display device drives liquid crystal of Twisted Nematic TN mode by a vertical electric field between a common electrode on an upper substrate and a pixel electrode on a lower substrate, wherein the common electrode faces with the pixel electrode. This vertical electric field applying mode liquid crystal display device has an advantage of high aperture ratio, while it has a disadvantage of narrow viewing angle.
The horizontal electric field applying mode liquid crystal display device drives liquid crystal of In-Plane Switching IPS mode by a horizontal electric field between the pixel and common electrodes formed on the lower substrate. This horizontal electric field applying mode has an advantage of wide viewing angle.
Also, the liquid crystal display device may be largely classified into a transmitting type liquid crystal display device using light generated from a backlight unit, and a reflective type liquid crystal display device using ambient and surrounding light. The transmitting type liquid crystal display device has a disadvantage of large power consumption. The reflective type liquid crystal display device can not display desired images in the dark surroundings because the reflective type liquid crystal display device uses the ambient and surrounding light.
To overcome these problems, there are studies and developments for a transflective (transmitting reflective) type liquid crystal display device. The transflective type liquid crystal display device can be operated by both a transmitting mode and a reflective mode since the transflective type liquid crystal display device is provided with both a transmitting part and a reflective part, to thereby use both the transmitting light from the backlight unit and the ambient and surrounding light. That is, the transflective type liquid crystal display device is operated by the reflective mode if there is a sufficient amount of ambient and surrounding light. Meanwhile, the transflective type liquid crystal display device is operated by the transmitting mode using the transmitting light generated from the backlight unit if there is an insufficient amount of ambient and surrounding light. Thus, the transflective type liquid crystal display device can decrease the power consumption as compared with that of the transmitting type liquid crystal display device. In addition, unlike the reflective type liquid crystal display device, the transflective type liquid crystal display device is free from limitations of the ambient and surrounding light.
Hereinafter, a related art transflective type liquid crystal display device and a structure and operation thereof will be explained with reference to FIG. 1.
As shown in FIG. 1, the related art transflective type liquid crystal display device includes a transmitting part and a reflective part in each pixel region, which is driven by both a vertical electric field and a horizontal electric field. As shown in FIG. 1, the transflective type liquid crystal display device is comprised of a thin film transistor substrate 11 including a plurality of lines and thin film transistors; a color filter substrate 21 facing the thin film transistor substrate 11; and a liquid crystal layer 16 formed between the thin film transistor substrate 11 and the color filter substrate 21.
The thin film transistor substrate 11 includes gate and data lines crossing each other to define a pixel region; a thin film transistor formed adjacent to a crossing portion of the gate and data lines; an organic insulation film 18 formed in the reflective part; a reflective electrode 6, formed on the organic insulation film 18, for reflecting incident light from the external; a pixel electrode 17 formed as the same layer as the reflective electrode 60 in the transmitting part; a passivation film 19 for covering the reflective electrode 60 and the pixel electrode 17; and a common electrode 24, formed on the passivation film 19, for forming a horizontal electric field with the pixel electrode 17.
At this time, the related art transflective type horizontal electric field mode liquid crystal display device has a cell gap in the transmitting part, which is about twice as large as a cell gap in the reflective part due to the organic insulation film 60 formed in the reflective part, so that it is possible to compensate for a phase difference between the reflective part and the transmitting part, thereby achieving the uniform luminance property in the pixel region.
To form the dual cell gap structure for achievement of the uniform luminance property in the pixel region, it requires an additional step for forming the organic insulation film 60 in the reflective part, thereby causing the complicated process and low efficiency.
In order to solve the problem of the transflective type liquid crystal display device having the dual cell gap structure, there are studies and researches for a transflective type liquid crystal display device having a single cell gap structure by removing a step difference between the transmitting and reflective parts of the pixel region with the use of an organic insulation material having the great step-difference compensation property.
In case of the transflective type liquid crystal display device having the single cell gap structure, as shown in FIG. 2, a reflective curve of reflective part and a transmitting curve of transmitting part are not matched up due to a difference of effective refraction index of liquid crystal between the reflective part and the transmitting part. Accordingly, it is difficult to match up the reflective curve of reflective part and the transmitting curve of transmitting part in the related art transflective type liquid crystal display panel having the single cell gap structure, whereby the reflective part and the transmitting part for constituting the pixel region have the different gray scales.